diff --git a/lib/algorithms/iterative/ImplicitlyRestartedLanczos.h b/lib/algorithms/iterative/ImplicitlyRestartedLanczos.h
index 8011e796..cee566e6 100644
--- a/lib/algorithms/iterative/ImplicitlyRestartedLanczos.h
+++ b/lib/algorithms/iterative/ImplicitlyRestartedLanczos.h
@@ -57,8 +57,10 @@ void basisRotate(std::vector<Field> &basis,Eigen::MatrixXd& Qt,int j0, int j1, i
       
   parallel_region
   {
-    std::vector < vobj > B(Nm); // Thread private
-        
+    Vector < vobj > B; // Thread private
+
+    PARALLEL_CRITICAL { B.resize(Nm); }
+       
     parallel_for_internal(int ss=0;ss < grid->oSites();ss++){
       for(int j=j0; j<j1; ++j) B[j]=0.;